There has so far been marketed a disk player device dedicated to reproduction, such as a CD player designed to reproduce a so-called compact disk (CD), which is an optical disk on which audio signals such as the voice or musical sounds are recorded in the digitized form. While the conventional CD player is dedicated to reproduction, attempts have been made to develop a disk system which, through the use of a magneto-optical disk formed by a photo-magnetic recording medium allowing to rewriting of the information, is adapted for both recording and reproduction and for maintaining compatibility with respect to the compact disk. All the numbers or tunes on the compact disk are recorded end to end, such that the CD player continues its reproducing operation after a given number has been reproduced to proceed continuously to reproduce the next number.
As shown diagrammatically in FIG. 1, the recording disk 1 employed in the above disk system is formed with spirally extending pregrooves 2 each having a depth equal to .lambda./8, wherein .lambda. indicates the wavelength of the laser beam used for information recording. On a land 3 between the adjacent pregrooves 2, a prerecorded region 4 in which patterns of projections and recesses formed by pits each .lambda./4 in depth are previously recorded and a data recording region 5 in which magneto-optical recording is performed, are formed alternately in the circumferential direction, each at an equal pitch. A lead-in region 7 is provided at the inner periphery of the program region 6 in which the performance or play information is recorded. In this lead-in region, there is recorded a table of contents (TOC) information or catalog information indicating the record contents of the program region 6. In the prerecorded region 4 of the recording disk 1, there are recorded 24 bits of sync signals and 14 bits or 1 symbol of subcodes as patterns of projections and recesses formed in advance by a molding operation as indicated in FIG. 3. These subcodes represent the absolute time information or absolute addresses from the start position of the program region 6. The above 24 bit sync signals and 14 bit subcodes are a part of the 588 channel bit data making up one frame of the data format, as shown in FIG. 2, standardized for the compact disk (CD), and including, in addition to the above sync signals and subcodes, 14.times.32 bits (32 symbols)of the data such as the performance information and parities and margin bits, each of 3 bits, provided between adjacent symbols.
In a disk system employing the above described recording disk 1, disk rotation control etc. is performed at a constant linear velocity (CLV), using the aforementioned absolute addresses reproduced from the prerecorded region 4 of the recordable disk 1, so that the information is recorded in the data format standardized for the compact disk (CD).
It will be noted that, with the disk system adapted for both recording and reproduction and for maintaining superior compatibility with respect to the compact disk (CD), there is the risk that the play information previously recorded on the program region of the recording disk may be erased inadvertently or replaced by another play information by superscription. More in detail, in the above disk system, all of the play information is not necessarily recorded end to end on the disk, such that, when a new number is to be recorded on an unrecorded portion between first and second numbers, should the play time of the newly recorded number be longer than the recordable time for the unrecorded portion, the play data for the second number is replaced by the new play data. In the case of audio as video tape cassettes, to prevent such inadvertent erasure of the necessary data, rupturable tongues are provided to the cassett half as an inadvertent erasure inhibit means, which may be ruptured manually to inhibit recording or erasure on the tape in its entirety. However, in a disk system employing a recording disk, such as a magneto-optical disk having a larger recording capacity, should the recording or erasure of the disk be inhibited in its entirety, the risk is high that the volume of the unrecorded portion is increased, with the result that the utilization efficiency of the recordable disk is lowered.
In view of the, above problem, the present invention is aimed at providing a disk recording/reproducing apparatus and a disk recording/reproducing method in which a program region and a lead-in region are provided on a recording disk to which absolute addresses are imparted in advance, data such as play information are recorded in said program region, start address data and end address data of a unit information region in said program region having data recorded therein are recorded as table of contents data or catalog data in said lead-in region, and in which recording and/or reproduction in or from said program region is performed on the basis of said catalog data in said lead-in region, wherein the utilization efficiency of the recording disk is improved and wherein the erasure inhibit and erasure enable of each information unit of the prerecorded data in the program region may be commanded by an erasure inhibit flag.